21221091 has 12 divisors (see below), whose sum is σ = 31481632. Its totient is φ = 13764816.

The previous prime is 21221077. The next prime is 21221099. The reversal of 21221091 is 19012212.

It is not a de Polignac number, because 21221091 - 2⁷ = 21220963 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21221099) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 31531 + ... + 32196.

Almost surely, 2^21221091 is an apocalyptic number.

21221091 is a deficient number, since it is larger than the sum of its proper divisors (10260541).

21221091 is a wasteful number, since it uses less digits than its factorization.

21221091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 63770 (or 63767 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 18.

The square root of 21221091 is about 4606.6355401746. The cubic root of 21221091 is about 276.8572511455.

The spelling of 21221091 in words is "twenty-one million, two hundred twenty-one thousand, ninety-one".